Saturday, December 1, 2007
Catastrophic Structural Failure
Focusing on maintenance programs
One accident that failed to make the front pages occurred on May 9, 2005, when a student pilot and instructor were flying in the Kissimmee, Fla., area for a half-hour aerobatics lesson. The instructor had been demonstrating various maneuvers before the North American SNJ-6 airplane was seen entering a spin, descending rapidly and hitting the ground. Both occupants were killed. The airplane’s right wing had separated in flight. Investigators discovered that the outboard right-wing lower attachment bracket had failed because of fatigue cracking, resulting in separation of the wing. The FAA issued an Emergency Airworthiness Directive requiring fluorescent-dye-penetrant inspections of the wing-attach flanges at 200-hour intervals.
At the other end of the attention spectrum was the December 19, 2005, accident involving Chalk’s Ocean Airways flight 101, a Grumman Turbo Mallard amphibian. It had taken off from the Miami Seaplane Base in Florida on a regularly scheduled passenger flight to Bimini in the Bahamas. There were two pilots and 18 passengers on board. The seaplane base is on an island about two miles east of Miami. The water runway area is 15,000 feet long and 200 feet wide. The terminal on the island used by Chalk’s Ocean Airways was built in 1926.
About one minute after takeoff, the right wing separated, and the airplane crashed into a shipping channel adjacent to the Port of Miami. All on board were killed. The NTSB recently completed its investigation into the accident, which paid a lot of attention to the age and specialized nature of the aircraft, the operator’s maintenance programs and practices, and FAA oversight.
Things being the way they are in the world today, one of the first issues addressed was whether the crash involved terrorism or some other form of sabotage. A video taken by a witness who was on a beach showed the airplane in a nose-down attitude of between 35 and 45 degrees after the wing separated. It didn’t show smoke or debris coming from the airplane, but did show a cloud of fire and smoke behind it. A video taken by a U.S. Coast Guard surveillance camera showed the airplane passing over Miami Harbor and moving away from the camera’s position. As the airplane moved away, it also moved toward the center of the camera’s field of view and became progressively smaller. About nine seconds after the airplane had gone too far away for the camera to pick up, a bright flash appeared. Black smoke could be seen in the area where the flash appeared, and a smoke trail fell toward the water. Pieces of the recovered wreckage were sent to the FBI’s laboratory in Quantico, Va., and were screened for explosives and explosive residue. None were found.
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Labels: Accident Statistics, Columns, FAA Regulations, Features, Flight Hazards, Journeys, Maintenance, Safety